Servers and other devices in a computing network are typically identified by a numeric Internet Protocol (IP) address that might change over time and by a text-based domain name that might remain the same. The Domain Name System (DNS) is a system for mapping the text-based domain name for a web server or other computing device to the device's current numeric IP address. A DNS server or similar device can accept a domain name and provide the IP address that is currently associated with the name. A computer user wishing to connect to a particular server, such as a web server, can enter the domain name associated with the web server into a web browser. The domain name is then sent to a DNS server, which returns the IP address associated with that domain name to the browser. The browser can then use the IP address to connect to the web server. Similarly, the DNS might allow an automated computing device wishing to connect to another device to specify only the domain name of the other device rather than the IP address of the other device.
Several types of errors might prevent a request for a conversion from a domain name to an IP address from occurring successfully. In one type of error, the resolution of a domain name to an IP address may not take place due to the unavailability of a DNS server. The DNS server unavailability may be due to, for instance, a connection problem between the DNS server and a client, a hardware or software problem within the DNS server, or a denial of service attack on the DNS server. In another type of error, a DNS server may be available but may provide incorrect information. An invalid IP address might be returned from a DNS server when, for instance, a software error occurs in the DNS server, the DNS server is incorrectly configured, or invalid IP addresses have been inadvertently or maliciously entered into the DNS server in place of valid IP addresses.